1. Technical Field
The present invention relates to liquid ejecting heads such as ink jet recording heads that eject liquid droplets from nozzles by means of pressure variation.
2. Related Art
The liquid ejecting heads that eject liquid droplets from nozzles by varying a pressure of the liquid in a pressure chamber include, for example, ink jet recording heads (hereinafter simply referred to as recording heads) used for image recording apparatuses such as ink jet recording apparatuses (hereinafter simply referred to as printers), color material ejecting heads used for manufacturing color filters for liquid crystal displays and the like, electrode material ejecting heads used for forming electrodes for field emission displays (FEDs), organic electroluminescence (EL) displays and the like, and bioorganic ejecting heads used for manufacturing biochips.
One type of liquid ejecting head is configured to eject liquid droplets by deforming piezoelectric elements (a type of pressure generating element) which are bonded to a vibration plate. In this type of liquid ejecting head, a drive voltage (drive pulse) is applied to the piezoelectric elements so as to vary the volumes of pressure chambers, thereby varying the pressure of a liquid stored in the pressure chambers, allowing the droplets of liquid to be ejected through the nozzles.
Such piezoelectric elements are, for example, as disclosed in JP-A-2004-034293, electrically connected to a film type wiring member (hereinafter referred to as a flexible cable) such as COF (Chip On Film) and TCP (Tape Career Package) having a base film made of polyimide or the like, on which ICs for activating the piezoelectric elements are mounted, and configured such that a drive voltage is applied to the piezoelectric elements through the flexible cable. The piezoelectric element includes a lower electrode film, a piezoelectric layer and an upper electrode film. In general, one of the electrodes (e.g., lower electrode film) is formed as a common element electrode that is commonly used for a plurality of piezoelectric elements, and the other electrodes (e.g., upper electrode film) are formed as individual element electrodes that are individually patterned for the respective piezoelectric elements. The piezoelectric layer is interposed between the common element electrode and the individual element electrode and acts as a piezoelectric active unit that bends in response to a drive voltage applied across both electrodes.
In recent years, recording heads are preferred in which nozzles are closely arranged and lead wires led out from the pressure generating elements are extremely closely arranged next to each other and, accordingly, the lead wire width tends to be small. This may cause a problem, such as a connection failure due to short circuit between adjacent wires. Also, a flexible cable made of polyimide or the like may expand due to heat or moisture during bonding of wires to the piezoelectric elements. Specifically, the flexible cable expands in the terminal row direction, which is the longitudinal direction of the row of terminals. As a result, it may be displaced from a predetermined connection position between the flexible cable terminals and the pressure generating element terminals, thereby causing a connection failure.
Further, a crack checking pattern for detecting a crack in a vibration plate is disposed on the vibration plate. The crack checking pattern is formed electrically independently from the common element electrode and the individual element electrode, and disposed on the vibration plate, which overlies the flow channel forming substrate having liquid passages such as pressure chambers, at the outer side relative to the terminal row of the pressure generating element. However, the widths of the crack checking pattern and the lead wires led out from the crack checking pattern both tend to be small, which makes it difficult to ensure the reliability in connection with the terminals of the flexible cable.